#menu-dung, .sub-menu {
    list-style: none;
    padding: 0;
    margin: 0;
    background-color: #000000; 
    width: 150px;
    border: 0.5px solid #FFF;
}

#menu-dung li {
    position: relative; 
    border-bottom: 1px solid #FFF;
}

#menu-dung li a {
    display: block;
    padding: 12px 15px;
    color: #FFF;
    text-decoration: none;
    font-weight: bold;
    font-size: 13px;
}

/* Hiệu ứng khi rê chuột qua */
#menu-dung li a:hover {
    background-color: darkgray;
}


.active-gray {
    background-color: darkgray !important;
    color: white !important;
}

/* Cấp 2 và Cấp 3 */
.sub-menu {
    position: absolute;
    top: -1px;      
    left: 100%;   
    width: max-content; 
    min-width: 150px;
    display: none;  
    z-index: 100;
}


li:hover > .sub-menu {
    display: block;
}